Printed wiring card mountable reed switch

ABSTRACT

A magnetic latching reed switch is provided with an improved bobbin having a plurality of coil terminals disposed in a bottom flange or base. On terminal of each reed capsule inserted in the bobbin extends beneath the base and the other is welded to a return strap which also extends through the base such that the switch terminals and coil terminals are adapted to engage a corresponding pattern of apertures in a printed wiring car. A plurality of reed switches are thus supported by the wiring card which also provides all internal switch wiring.

United States Patent Miknaitis PRINTED WIRING CARD MOUNTABLE REED SWITCH Jan. 1, 1974 3,500,267 3/1970 Wasserman 335/153 Primary Examiner-Roy N. Envall, .lr. Attorney-K. Mullerheim et'al.

[5 7 ABSTRACT V A magnetic latching reed switch is provided with an improved bobbin having a plurality of coil terminals disposed in a bottom flange or base. On terminal of each reed capsule inserted in the bobbin extends beneath the base and the other is welded to a return strap which also extends through the base such that the switch terminals and coil terminals are adapted to engage a corresponding pattern of apertures in a printed wiring car. A plurality of reed switches are thus supported by the wiring card which also provides all internal switch wiring.

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PATENIEDJAN 11w 3 783 421- sum 3 M3 1 PRINTED WIRING CARD MOUNTABLE REED SWITCH BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention-relates generally to the field of electromagnetic switches and more particularly to a new and improved magnetic latching reed switch construction.

2. Description of the Prior Art In modern telephone systems the reed switch has found wide acceptance as a crosspoint in switching matrices. Prior to the present invention it has generally been the practice to form a crosspoint matrix by mounting a large plurality of reed switch control coils through a single magnetic shunt plate. For illustrations of this approach reference may be had to U.S. Pat. No. 3,431,520 which issued to W. A. Lindenberger on Mar. 4, 1969 and U.S. Pat. 3,500,267 which issued to N.- Wasserman on Mar. 10, 1970. The basic operation of this type of switch is also described in an article entitled Operation of the Fereed Switch by Sol D. Levine which appeared in the October, 1965 issue of The Western Electric Engineer, pp 24-25.

Although the shunt plate-mounted crosspoint matrix has been found to operate satisfactorily in many applications, it has several features which complicate its manufacture. Specifically the shunt plate in constituting the mechanical support for the" individual crosspoints acts to separate each coil into two isolated ends thereby requiring the use of numerous tie posts through or around the shunt plate in order tov transfer the coil and switch leads to one terminal side. Alternatively, wiring to the switch must be provided on both sides of the shunt plate. Internal switch connections as well as external connections to the switches are then accomplished via hard wiring or by two wiring cards. This approach serves to complicate the coil winding, switch assembly, and wiring processes.

OBJECTS AND SUMMARY OF THE INVENTION From the preceding discussion it will be understood that among the various objectives of the present invention are included the following:

the provision of an improved reed switch construction, and

the provision of apparatus of the above-described character which is adapted for direct connection in assembled form with a single printed. wiring card.

These and other, objectives ofthe present invention are efficiently met by providing a reed switch wherein the control coil leads are connected to terminals which extend from the bottom o'fa flanged base portion of the bobbin. The reed switch leads also extend through the bottom of the base portion of the bobbin such that the terminals and switch leads may be inserted into a corresponding apertures in a printed wiringcard and tenninated to the circuits thereof.

The foregoing as well as other objects, features and. advantages of the present invention will become more apparent-from the following detailed description taken in conjunction with the various views of the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cut-away perspective view of a reed switch assembly in accordance with the principles of the present invention;

FIG. 2 is a partial cut-away perspective view of an alternative embodiment of the shunt plate portion of FIG. 1;

FIG. 3 is a bottom elevation view of the apparatus of FIG. 1;

FIG. 4 is a horizontal cross-section view taken along section line 4 of FIG. 1;

FIG. 5 is a horizontal cross-section view taken along section line 5 of FIG. 1; and

FIG. 6 is a partially exploded elevation view of a printed wiring card mounted crosspoint matrix incorporating a plurality of reed switch assemblies illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT sules is shown for the purposes of illustration it will be understood that the present invention contemplates both single capsule and multiple capsule embodiments as well.

The main component of the illustrated switch from a manufacturing point of view is the bobbin 10 which is typically molded from a suitable insulative thermoplastic material. The bobbin 10 has longitudinal channels 12 adapted to receive the reed capsules l4 and is provided with integrally formed circumferential spacers 16 for the control coils 18-24. A molded circumferential flange 26 adapted to receive and retain a magnetic shunt element 28 is also provided. The bottom end of the bobbin 10 is provided with a base 30 in which a plurality of terminals 32 are inserted for terminating the leads from the control coils as will be hereinafter described. The bottom leads 34 from the reed capsules 14 extend through apertures 36 in, and beyond the lower extremity of, the base 30. L shaped return straps 38 are attached to the upper leads 40 of the reed capsules 14 and extend downwardly along the outside of the bobbin 10, passing through an aperture in the base 30. The reed capsules 14 are retained within the bobbin 10 by a removable, press fitted retainer 42 placed over the top of bobbin 10. The horizontal section lines 3, 4 and 5 refer to the views of the apparatus of FIG. 1 shown in corresponding figures to be presently discussed.

In the apparatus of FIG. I the magnetic shunt element 28 is illustrated as being insert-molded within the circumferential flange 26 at the substantial midpoint of the bobbin 10. The partial cut-away perspective view of FIG. 2 illustrates an alternative embodiment wherein a transverse aperture 26' is disposed through the molded bobbin into which the magnetic shunt element 28 may be snapped prior to insertion of the reedcapsules. With this type of construction the bobbin molding process may be further simplified by eliminating the need to insert-mold the shunt element.

It is known in the magnetic reed switch art that a magnetic shunt is needed to improve the magnetic control of the latching reeds, particularly during the switch release function. The reed switch of the present invention employs an individual shunt element 28 rather than the single extended shunt plate used to support a plurality of switches in prior art switch matrices. It will be seen from FIG. 1. that all electrical connections to the switch, both to the coils 18-24 via terminals 32 and to the reed capsules 14 via leads 34 and return straps 38, are made at the base 30 of the bobbin 10. With this construction the switch is particularly well adapted for mounting on and connection to a printed wiring card (not shown). A printed wiring card thus provides the mechanical support for the switch and, for a switch matrix, provides very convenient means for wiring the switches to other matrix components and all the components may be terminated to the printed wiring card in a single operation such as by wave soldering.

FIG. 3 is a bottom elevation view of the switch of FIG. 1 and more clearly illustrates the preferred configuration of the bobbin base 30. The base is provided at opposed sides with outwardly extending tabs 44, each having an aperture 46 which is adapted to receive and retain the reed capsule return strap 38. Since the reed capsules l4 typically closely fit the longitudinal channels in the bobbin and the return straps 38 are attached to the upper reed capsule leads, by passing the lower end of each return strap 38 through the bobbin base 30 they are adequately positioned along the length of the bobbin such as to avoid contact with the coil windings and shunt element. FIG. 3 also illustrates the pattern of termination apertures to be provided in the printed wiring card (not shown) to which the switch is to be mounted. 1

In the embodiment shown in FIG. 1 the bobbin base will be provided with a total of five terminals 32 -32 as shown in FIG. 3. Terminals 32,-32 extend both laterally outward from the base for ease of wire termination and longitudinally downward to facilitate terminais assumed to be a counterclockwise direction for purposes of illustration. The wire is then attached to common terminal 32 and then to terminal 32 prior to winding lower secondary coil 24 in a counterclockwise direction. The wire is then fed upward through channel 5 2 and the upper primary coil 18 is then wound in the clockwise direction. The wire is then fed downward through channel 52 and attached to terminal 32 and thence to terminal 32 The coil wire is then again fed upward through channel 52 on the opposite side of shunt plate 28 and the upper secondary coil 20 is wound in a counterclockwise direction. The wire is then returned downward through channel 52 and terminated on common terminal 32 In this fashion the coils 18-24 are easily wound from a single length of coil wire without crossovers and are then separated by simply removing the strap between terminals 32, and 32 and between terminals 32 and 32 The five terminations are then soldered to complete the coil installation process. The reed capsule-return strap subassemblies are then inserted and the retaining ring installed.

FIG. 4 is a top view .of the switch of FIG. 1 illustrating the manner in which the reed capsule return straps 38 are connected to the upper reed capsule leads 40. The upper end of the bobbin 10 is provided with diagonal slots which are adapted to receive the transverse portion of the L shaped return straps 38. The return straps 38 are attached such as by welding to the reed capsule leads 40 and extend to a point outside the bobbin 10 where they are bent at right angles to extend longitudinally downward along opposed sides.

FIG. 5 is a horizontal cross-section view along section line 5 of FIG. 1 and illustrates the configuration of the individual magnetic shunt element 28 used with that switch. The shunt element is of a generally flat, oval overall shape, and has locating notches at each end which are adapted to receive portions of the circumferential supporting flange 26 of bobbin 10. It is also provided with opposed open channels 52 to allow passage of the reed capsule return straps 38 and control coil leads. A central aperture 54 is of a configuration adapted to allow insertion of the reed capsules 14.

FIG. 6 is a partially exploded perspective view of a printed wiring card mounted crosspoint switch matrix using switches of the type shown in FIG. 1. Mechanical support as well as all component wiring is provided by a printed wiring card 56 to which the reed switches 58 and other matrix components 60 are terminated. For each switch the wiring card 56 is provided with an appropriate wiring pattern 62 which extends from aconnector end 64 to each of a plurality of apertures 66 which are arranged in a pattern adapted to receive the coil terminals, reed capsule leads, and return straps of the switch. All of the components are inserted into the wiring card and the entire assembly may be soldered using conventional techniques. The return straps attached to each reed capsule position and retain the capsules during the soldering process and provide for convenient replacement of any faulty capsules. It will be seen that only two solder connections need be unsoldered to remove the capsule-strap subassembly.

Since matrix cards can become quite heavy it is preferred in the practice of this invention to provide a metal cover 68 for the matrix assembly. This cover may conveniently be attached to the printed wiring card 56 by screws 70 and provides a mounting for a card insertion/extraction handle 72. When attached to the wiring card 56 the cover provides additional structural support for the card as well as electromagnetic shielding of the matrix.

From the preceding description it will be seen that the Applicant has provided a new and novel wiring card mountable reed switch construction whereby the objectives set forth hereinabove are efficiently met. Since certain changes in the above described construction will occur to those skilled in the art without departure from the scope of the invention it is intended that all matter set forth in the above description or shown in the'appended drawings shall be interpreted as illustrative and not in any limiting sense.

Having described what is new and novel and desired to secure by letters Patent, what is claimed is: ;8c

1. A magnetic latching reed switch comprising a magnetic shunt element,

an insulative bobbin having a base portion, a longitudinal channel therein, and a circumferential shunt element supporting means formed therein at the substantial midpoint of said channel, said bobbin is formed of a thermoplastic material and said magnetic shunt element is insert molded within said supporting means, I

a reedcapsule switching element disposed in said longitudinal channel and through said shunt element, having a first electrical lead extending through said base portion, a second electrical lead extending upward from said bobbin, and overlapping switching contacts in substantial alignment with said shunt element,

a first differentially wound control coil disposed about said bobbin adjacent one side of said shunt element supporting means,

a second differentially wound control coil disposed about said bobbin adjacent the other side of said shunt element supporting means,

a plurality of electrically conductive terminals disposed through said bobbin base portion, connected at one end thereof to said controlcoils and extending at the other end from the bottom of said bobbin base portion,

a reedcapsule return strap connected at one end to the second electrical lead of said reedcapsule switching element, extending longitudinally downward adjacent the exterior of said coils, passing through said bobbin base portion, and extending from the bottom thereof, and

said first electrical lead from said reedcapsule, said plurality of electrically conductive terminals, and said return strap extending from the bottom of said bobbin base in a preselected termination pattern.

2. A switch as recited in claim 1 further including an insulative circumferential retainer disposed about and frictionally engaging said bobbin for retaining said reedcapsule and said return strap in a fixed position with respect to said bobbin.

3. A switch as recited in claim 1 further including a printed wiring card having'a plurality of circuits thereon and a like plurality of apertures disposed therethrough in a pattern corresponding to said preselected termination pattern,

said first reedcapsule lead, said conductive terminals and said return strap extending through said apertures and being electrically connected to a corresponding circuit of said wiring card. 4. A switch as recited in claim 3 further including a cover rigidly affixed to the periphery of said printed wiring card to thereby enclose said reed switch and structurally reinforce said wiring card. 5. A switch as recited in claim 4 further including a handle affixed to said cover.

6. A magnetic latching reed switch comprising a magnetic shunt element,

an insulative bobbin having a base portion, a longitudinal channel therein, and a circumferential shunt element supporting means formed therein at the substantial midpoint of said channel, said magnetic shunt element supporting means comprises a transverse aperture formed in said bobbin and adapted to receive and frictionally engage said shunt element,

a reedcapsule switching element disposed in said longitudinal channel and through said shunt element, having a first electrical lead extending through said base portion, a second electrical lead extending upward from said bobbin, and overlapping switching contacts in substantial alignment with said shunt element,

a first differentially wound control coil disposed about said bobbin adjacent one side of said shunt element supporting means,

a second differentially wound control coil disposed about said bobbin adjacent the other side of said shunt element supporting means,

a plurality of electrically conductive terminals disposed through said bobbin base portion, connected at one end thereof to said control coils and extending at the other end from the bottom of said bobbin base portion, I

a reedcapsule return strap connected at one end to the second electrical lead of said reedcapsule switching element, extending longitudinally downward adjacent the exterior of said coils, passing through said bobbin base portion, and extending from the bottom thereof, and

said first electrical lead from said reedcapsule, said plurality of electrically conductive terminals, and said return strap extending from the bottom of said bobbin base in a preselected termination pattern. 

1. A magnetic latching reed switch comprising a magnetic shunt element, an insulative bobbin having a base portion, a longitudinal channel therein, and a circumferential shunt element supporting means formed therein at the substantial midpoint of said channel, said bobbin is formed of a thermoplastic material and said magnetic shunt element is insert molded within said supporting means, a reedcapsule switching element disposed in said longitudinal channel and through said shunt element, having a first electrical lead extending through said base portion, a second electrical lead extending upward from said bobbin, and overlapping switching contacts in substantial alignment with said shunt element, a first differentially wound control coil disposed about said bobbin adjacent one side of said shunt element supporting means, a second differentially wound control coil disposed about said bobbin adjacent the other side of said shunt element supporting means, a plurality of electrically conductive terminals disposed through said bobbin base portion, connected at one end thereof to said control coils and extending at the other end from the bottom of said bobbin base portion, a reedcapsule return strap connected at one end to the second electrical lead of said reedcapsule switching element, extending longitudinally downward adjacent the exterior of said coils, passing through said bobbin base portion, and extending from the bottom thereof, and said first electrical lead from said reedcapsule, said plurality of electrically conductive terminals, and said return strap extending from the bottom of said bobbin base in a preselected termination pattern.
 2. A switch as recited in claim 1 further including an insulative circumferential retainer disposed about and frictionally engaging said bobbin for retaining said reedcapsule and said return strap in a fixed position with respect to said bobbin.
 3. A switch as recited in claim 1 further including a printed wiring card having a plurality of circuits thereon and a like plurality of apertures disposed therethrough in a pattern corresponding to said preselected termination pattern, said first reedcapsule lead, said conductive terminals and said return strap extending through said apertures and being electrically connected to a corresponding circuit of said wiring card.
 4. A switch as recited in claim 3 further including a cover rigidly affixed to the periphery of said printed wiring card to thereby enclose said reed switch and structurally reinforce said wiring card.
 5. A switch as recited in claim 4 further including a handle affixed to said cover.
 6. A magnetic latching reed switch comprising a magnetic shunt element, an insulative bobbin having a base portion, a longitudinal channel therein, and a circumferential shunt element supporting means formed therein at the substantial midpoint of said channel, said magnetic shunt element supporting means comprises a transverse aperture formed in said bobbin and adapted to receive and frictionally engage said shunt element, a reedcapsule switching element disposed in said longitudinal channel and through said shunt element, having a first electrical lead extending through said base portion, a second electrical lead extending upward from said bobbin, and overlapping switching contacts in substantial alignment with said shunt element, a first differentially wound control coil disposed about said bobbin adjacent one side of said shunt element supporting means, a second differentially wound control coil disposed about said bobbin adjacent the other side of said shunt element supporting means, a plurality of electrically conductive terminals disposed through said bobbin base portion, connected at one end thereof to said control coils and extending at the other end from the bottom of said bobbin base portion, a reedcapsule return strap connected at one end to the second electrical lead of said reedcapsule switching element, extending longitudinally downward adjacent the exterior of said coils, passing through said bobbin base portion, and extending from the bottom thereof, and said first electrical lead from said reedcapsule, said plurality of electrically conductive terminals, and said return strap extending from the bottom of said bobbin base in a preselected termination pattern. 